The present invention relates to improvements in methods of and in apparatus for preserving goods which are confined in containers, particularly to improvements in methods of and in apparatus for preserving foodstuffs which are confined in substantially cup-shaped containers.
It is known to confine foodstuffs (e.g., salads or edibles which contain milk) in containers wherein the open top of the container is surrounded by a rim and the open top is sealed by a closure in the form of a metallic or plastic foil which is bonded to or is otherwise sealingly affixed to the rim. The storage life of foodstuffs in such containers depends on the extent to which the containers are filled, i.e., on the quantity of air which is entrapped in the sealed containers. In accordance with a presently known proposal, sealing of containers which contain metered or randomly selected quantities of perishable goods (such as foodstuffs) takes place in rooms wherein the composition of gases is selected, monitored and regulated with a view to ensure that the sealed containers will contain minimal quantities of oxygen. A drawback of such proposal is that the sealing of containers is a very expensive operation, mainly (or to a considerable extent) because the freshly filled containers entrain certain quantities of air into the room where the sealing operation takes place and, therefore, it is necessary to continuously withdraw air from the room and replace the withdrawn air with an inert gas which is not likely to adversely affect the storage life of the confined goods.
The situation is analogous if the containers which have received selected quantities of perishable goods are sealed in vacuo, i.e., such mode of evacuating air from containers is just as expensive as the establishment of a large room which accommodates the entire sealing apparatus and contains an inert gas or a mixture of inert gases at a predetermined temperature and pressure.
In accordance with a further prior proposal, perishable goods in cup-shaped or like containers are mixed with a medium which expels air from the containers not later than at the sealing station. A serious drawback of such proposal is that the medium which is admixed to perishable goods affects the quality and/or other desirable characteristics (such as the appearance) of goods in the containers. For example, the medium which is to expel air often causes foaming which changes the appearance of confined goods and renders them less palatable to consumers. Moreover, many types of perishable goods are likely to react with the admixed air expelling medium or media, and the condition of many perishable goods is likely to be changed solely as a result of mixing irrespective of the composition and/or nature of the medium or media which are to expel air. Still further, mixing of perishable goods with an air expelling medium will not always ensure adequate expulsion of air, even if one disregards the drawbacks of such procedure as concerns the appearance and/or quality of goods. Still further, mixing of goods with air expelling substances necessitates a substantial increase of bulk of container sealing apparatus. Last but not least, all heretofore known procedures exhibit the drawback that the percentage of air in confined goods is reduced (normally to about ten percent of the original volume) but not sufficiently to guarantee a relatively long storage life, for example, as known in connection with the canning of sardines and like foods in metallic containers which contain perishable foodstuffs and oil or another flowable substance which completely fills the sealed cans.